The overall objective of this work will continue to be the improvement of immunization against cholera by the development of more effective immunizing procedures and the study of the mode of action of antibacterial and antitoxic immunity. Additional studies are planed on the antigenic and secondary structure of cholera toxin. Using Chinese hamster ovary cells, further studies on the relationship of structure to function are planned. Toxin modification studies, using glutaraldehyde, formaldehyde, and heat will be done. The products will be tested for toxicity, antigenicity, and immunogenicity. Study of the relationship between cholera toxin and Salmonella toxin will be pursued. BIBLIOGRAPHIC REFERENCES: Sandefur, P.D. and J.W. Peterson. 1976. Neutralization of Salmonella toxin induced elongation of Chinese hamster ovary cells by cholera antitoxin. Infection and Immunity, in press. Sandefur, P.D. and J.W. Peterson. 1976. Skin permeability factors from culture filtrates of Salmonella species. In Proc. Twelfth Joint Conference on Cholera (1976), The United States - Japan Cooperative Medical Science program, in press.